Promote the performance of carbon electrode based perovskite solar cells with Cu2GeS3 hole transporting layer

Hole transporting layer (HTL) is indispensable for promoting the power conversion efficiency (PCE) and device stability of perovskite solar cells (PSCs), especially for the carbon electrode based PSCs (C-PSCs). Compared with the large amount of organic HTLs, which are available for metal electrode based PSCs, the inorganic HTLs for C-PSCs are relatively scarce. In this study, we successfully synthesized Cu2GeS3 nanocrystals with spherical shape and well dispersibility, and further explore their potential to function as inorganic HTL for C-PSCs. The Cu2GeS3 HTL can greatly improve the PCE of C-PSCs to 19.0 %, which is enhanced by 36.3 % compared with that (PCE = 13.9 %) of HTL-free C-PSCs. The reported PCE in our study is among the highest PCEs for C-PSCs with inorganic HTL, therefore, our study indicates that Cu2GeS3 nanocrystals are excellent inorganic HTL for C-PSCs.